1. Field of the Invention
The present invention relates to the injection of solid waste materials into a molten salt reactor for flameless destruction. In particular, a cooled, insulated injector bore allows air entrained waste particles to be injected into the molten salt free from incineration or burning.
2. Description of Related Art
The development of environmentally acceptable methods for treatment and disposal of large quantities of solid waste materials has been a research goal of industry and DOE federal laboratories. The current method for disposal of solid wastes is incineration. This method of bulk destruction generates hazardous products from the incomplete combustion of organic material. Safe methods must be devised that can completely combust or treat hazardous and mixed wastes (i.e., waste containing both hazardous and radioactive components) in waste-processing plants.
Molten salt oxidation (MSO) technology is a thermal process that has the inherent capability of completely destroying organic constituents of mixed wastes, hazardous wastes, and energetic (explosive) materials. MSO is ideally suited to the destruction of organic waste in the form of gases, liquids, slurries, sludges, and solids on the order of a few millimeters or less. The process has been used for coal gasification and destroying hazardous organics including PCBs, TCE, mixed waste oils, and energetic (explosive) materials.
Solid waste streams have special requirements that are not addressed by conventional MSO processes. A method is needed to incorporate solid waste materials into MSO operations to provide for a flameless method of destruction. Solid waste materials require careful metering before injection because the particles rise to the top. Each particle must have a sufficient amount of oxygen and ample resonance time in the salt bath so as to completely react before reaching the top, where combustion or xe2x80x9cflashingxe2x80x9d will occur. A system that injects solids too rapidly into the salt bath will cause the bath to contain unsafe concentrations of waste particles resulting in incineration rather than flameless decomposition. In addition, the waste particles must remain below their charring temperature prior to injection into the bath.
This invention provides a means of injecting solids into a molten salt bath in an accurate and controlled manner that allows solid wastes to be effectively destroyed without incineration. This is accomplished by a specially designed insulated injector bore that uses cooled air to keep the waste particles at an optimum temperature to avoid burning, yet having a de minimus effect on the bath temperature.
The present invention is a method and a delivery system that allows small particles of solid waste materials to be safely injected into a molten salt reactor and destroyed. This invention allows solid waste particles to be fed directly into the molten salt bath by employing an injector that is submersed in the molten salt bath. The solid wastes that can be destroyed include a wide variety of organic and mixed waste materials, including crucible graphite, plutonium-contaminated leaded gloves, ion exchange resins, wood, paper products, plastics, and hospital wastes.
The waste materials are first ground into workable sizes, typically no larger than about 3 mm. Commercial grinders provide an easy, cost-effective way to reduce the size of these particles. Small particle size is necessary for two reasons: to create particles that can be feasibly metered and diluted with oxidant air, and to ensure that the particles are fully converted during their resonance time in the salt bath. Once the waste materials are reduced to small particles, they are stored in a hopper, accurately metered, diluted with an oxidant gas such as air, and injected into the molten salt reactor toward the bottom of the salt bath.
A metering assembly provides a convenient and accurate means of diluting the solid particles with oxidant air from an attached air line. A vibratory metering device is used to feed the waste particles to a horizontal eductor. Oxidant air flows through the eductor creating a slight suction (venturi) effect on the feeder. The waste particles are entrained with oxidant air in this manner, and the slight suction ensures that the flow is always moving towards the reactor. Accurate metering ensures that all the organic constituents will have a sufficient supply of oxygen to be fully converted into carbon dioxide, water, and nitrogen before reaching the top of the salt bath where oxidation occurs. Proper dilution is also a necessary safety precaution to prevent pressure build-up in the reactor, as gases are generated during chemical reactions that take place in the salt.
Once diluted, the air-entrained waste travels through a conveyor tube and is injected into the molten salt via an injector bore. In order to prevent the waste particles from charring or melting and forming by-products that would clog the injector, the waste must be kept cool prior to injection. To accomplish this, the injector bore is designed with a double-jacketed cooling baffle system in which a continuous flow of cool air circulates. Thermal insulation allows this system to keep the waste cool without significantly affecting the temperature of the molten salt.
The waste is injected near the bottom of the salt bath. Once inside the molten salt bath, the particles begin to float to the top. Injection at the bottom of the bath maximizes the particles"" resonance time in the salt and enables all of the organic components of the waste to react with the oxygen in the air. Gaseous waste products such as nitrogen, carbon dioxide, and water vapor are produced from the organic components, while the inorganic components are retained within the molten salt as oxides, metals, or salts and later disposed of after further clean-up.
An objective of the present invention is to provide a method and apparatus to inject cooled solid waste into a molten salt bath to be effectively destroyed without incineration. Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings.